TC646
5.0
TYPICAL APPLICATIONS
Designing with the TC646 involves the following:
(1) The temperature sensor network must be
configured to deliver 1.25V to 2.65V on V
IN
for 0%
to 100% of the temperature range to be regulated.
(2) The auto-shutdown temperature must be set
with a voltage divider on V
AS
.
(3) The output drive transistor and associated circuitry
must be selected.
(4) The SENSE network, R
SENSE
and C
SENSE
, must
be designed for maximum efficiency while
delivering adequate signal amplitude.
(5) If shutdown capability is desired, the drive require-
ments of the external signal or circuit must be
considered.
+5V*
The TC642 demonstration and prototyping board
(TC642DEMO) and the TC642 Evaluation Kit
(TC642EV) provide working examples of TC646 cir-
cuits and prototyping aids. The TC642DEMO is a
printed circuit board optimized for small size and ease
of inclusion into system prototypes. The TC642EV is a
larger board intended for benchtop development and
analysis. At the very least, anyone contemplating a
design using the TC646 should consult the documen-
tation for both TC642EV (DS21403) and TC642DEMO
(DS21401). Figure 5-1 shows the base schematic for
the TC642DEMO.
C
B
1µF
R
1
NTC
8
Shutdown**
R
2
+5V
1
C
B
0.01µF
FAULT
V
IN
V
DD
6
Thermal
Shutdown
R
BASE
+12V
Fan
Q
1
TC646
R
3
3
V
AS
C
B
0.01µF
2
R
4
C
F
1µF
C
F
GND
4
V
OUT
7
5
SENSE
C
SENSE
R
SENSE
NOTES:
*See cautions regarding latch-up considerations in Section 5.0, "Typical Applications".
**Optional. See Section 5.0, "Typical Applications", for details.
FIGURE 5-1:
Typical Application Circuit.
DS21446C-page 10
2002 Microchip Technology Inc.
MICROCHIP [ MICROCHIP TECHNOLOGY ]
